1. Field of the Invention
The present invention relates to a color filter substrate and a liquid crystal display panel comprising the same, and more particularly, to a color filter substrate including a conductive column spacer.
2. Discussion of the Background
Since a liquid crystal display (LCD) has advantages over a conventional cathode ray tube (CRT), such that it may be thinner and lighter while having a larger screen, it has been widely developed. Further, since the LCD has been used in laptop and desktop computers, large-sized displays and mobile communication devices, its use has rapidly spread. Generally, an LCD adjusts an amount of light transmitted in accordance with image signals applied to control switches arrayed in a matrix to display a desired image on an LCD panel.
FIG. 1 is an equivalent circuit diagram of a unit pixel in a general LCD. Referring to FIG. 1, the unit pixel includes a thin film transistor (TFT) 13 serving as a switching element, a pixel electrode 14 for applying a voltage to a liquid crystal, and a storage capacitor Cs for maintaining the level of a liquid crystal voltage for a period of one frame. In such an LCD, when applying a gate drive voltage to a selected gate line 11, the TFT 13 connected to the gate line 11 turns on. At this time, a data voltage Vd is applied to the pixel electrode 14 while being charged to a liquid crystal cell capacitor Clc and the storage capacitor Cs through the TFT via a data line 12. The pixel electrode is maintained at the data voltage level until it is refreshed in the next frame.
FIG. 2A is a schematic sectional view of a conventional color filter substrate, and FIG. 2B is a schematic sectional view of a conventional LCD. Referring to FIG. 2A, a black matrix 22 is formed on an insulating transparent substrate 21. Red (R), blue (B) and green (G) color filters 23 are formed on the black matrix 22, and an overcoat layer 24 is formed on the color filters 23. A common electrode 25 is formed on the overcoat layer 24, and column spacers 26, which maintain a liquid crystal cell gap, are formed at a predetermined interval on the common electrode 25.
Referring to FIG. 2B, the color filter substrate of FIG. 2A is shown coupled with a thin film transistor substrate. The thin film transistor substrate includes a thin film transistor, a storage electrode 33, and a pixel electrode 39, and the column spacers 26 are disposed between the color filter substrate and the thin film transistor substrate to maintain the liquid crystal cell gap.
In such an LCD, a voltage (hereinafter, referred to as a common voltage) may be applied to the common electrode 25 of the color filter substrate through a short (not shown) formed at an edge of the thin film transistor substrate. Further, a voltage (hereinafter, referred to as a storage capacitor voltage) may be applied to the storage electrode 33 of the thin film transistor substrate through a storage electrode line coupled with the storage electrode 33 at the left and right sides of the thin film transistor substrate. As described above, since the common voltage and the storage capacitor voltage may be applied at peripheral portions of a substrate, their values at the edge of the substrate may differ from their values at the center of the substrate. Accordingly, problems such as a greenish color being displayed, flicker, and horizontal crosstalk may occur.
FIG. 3A is a diagram showing a conventional inversion driving method of unit pixels of the LCD, and FIG. 3B is a diagram showing a greenish color that may be displayed at the center of the LCD. FIG. 3A shows a 2×1 inversion driving method for inverting the polarity every two gate line selections, and FIG. 3B shows the greenish colored display occurring at the center of the LCD driven by 2×1 inversion driving. This problem typically occurs due to a large variation between the common voltage and the storage capacitor voltage at the center of the substrate.